The European Space Agency GEOS 2 spacecraft happened to cross the magnetopause several times at various local times. Intense electric and magnetic fluctuations, in the ultralow-frequency (ULF) range (0--10 Hz) have been detected during each such crossing, with a peak at the magnetopause and still large amplitudes in the adjacent magnetosheath and magnetopause boundary layer. By applying spectral analysis and correlations to the electric and magnetic fluctuations, and a minimum variance analysis to the magnetic fluctuations, we investigate the nature of these fluctuations which appear as short-lasting bursts in the spacecraft frame. Having reviewed possible interpretations, we show that the observed electric and magnetic signatures are consistent with small-scale (L≈ion Larmor radius) Alfvenic field-aligned structures passing by the spacecraft at high speed. It is suggested that these structures correspond to nonlinear Alfvenic structures. ¿ American Geophysical Union 1989